Shenzhen was not prepared for the heavy rains which caused deaths and disasters in May, 2014.
A:helpful
B:useful
C:ready
右侧漫画体现我国粮食资源的现状是( )
已知e1→=(2,1),e2→=(1,3),a→=(-1,2),若a→=λ1e1→+λ2e2→,则实数对(λ1,λ2)为( )